Australians Samantha Stosur and Daria Gavrilova have been eliminated in the third round of the WTA event in Charleston.
Stosur's serve again proved problematic against Italian Sara Errani and was broken in eight of her 11 service games en route to the 6-4 7-6 (7-5) loss.
The No.10 seed and 2010 Charleston champion won just 23 of 66 points on her own serve and only managed to stay in the second set when she broke Errani twice.
Gavrilova then went down in straight sets to American Sloane Stephens in an hour and 32 minutes, losing 6-4 6-3.
World No.37 Gavrilova broke Stephens just once on the clay court, with her defeat meaning there are no Australians left in the main draw.
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Stephens will go on to play Russia's Daria Kasatina in the quarter-finals, while Errani will face Yulia Putintseva of Kazakhstan, who shocked Venus Williams in the third round.
Williams, seeded third and ranked 14th in the world, had a chance to gain a place in the top 10 had she beaten Putintseva
Instead, the Kazakh won five of the final six games on Thursday (Friday AEST) to advance 7-6 (7-5) 2-6 6-4.
Williams became the fifth of the top eight seeds in Charleston to lose before the quarter-finals.
Top-seeded Angelique Kerber avoided that earlier in the day with a 6-2 6-3 victory over Slovakia's Kristina Kucova.
Kerber is the defending champion after winning the title in last year's Family Circle Cup. The second-ranked German star was not at her best, but good enough to put away Kucova. Kerber broke her opponent seven times, including the final game.
